Milk protein can be divided into rapid, moderate or late onset according to the time of the attack. 1. Rapid onset is less than 1 hour, meaning that a small dose can lead to an attack, and the allergic reaction is heavy, usually mainly manifesting as skin symptoms; 2. Moderate onset is 1-24 hours, and the typical symptoms usually appear after 6-8 hours, mainly manifesting in the gastrointestinal tract; 3. The onset is greater than 24 hours, this reaction is lighter, can tolerate the normal dose, clinical manifestations are mainly in the skin or the respiratory tract.